Extraction of sulfur compounds with thiolsulfonic esters



Dec. 29, 1953 w. F. WOLFF EIAL EXTRACTION OF SULFUR COMPOUNDS WITH THIOLSULFONIC ESTERS Filed Aug. 30, 1951 Carl E. ohnson INVENTORS: William F. Wolff ATTORNEY Juutxm 9:52:00 I Stam Ow AT 2 EQQES 2 w S M JX V 3.30% 2323292 A 2238 2ocb Exm Patented Dec. 29, 1953 -=2;'664,3 5 1-,EXTRA-QEI0N or SULFUR-GOMPOUNIIS w T sHiQt William 'Wolfi"; Park Johnson, Griifith lnd :Oil Company, Chicag Indiana ULFoNIdEs-Tms Forest, Ill., and on1 Appl c Au u t 30, Sr N9$4f$37 I 16 Claims.

"This invention relates to processes for the extraction of organic sulfur compounds from mixtures thereof with hydrocarbons, for example, such mixtures as occur in various processed-or unprocessed petroleum-oils. More particularly, this invention relates toprocesses for the se1ective extraction of organic sulfur compounds from oils comprising aliphatic hydrocarbons by the employment of certain thiolsulfonic esters as selective extraction solvents.

*-Numerous -so-called selective --so1vents have been proposed for removing organic sulfur compounds from their solutions in various hydrocarbon oils, particularly for the refining of lubricating oil stocks, burning oils and the like. While a number of selective solvents are in actualcommercialuse, no solvent has been found "to be suiliciently satisfactory forall purposes to retard the general search for improved selective solvents.

Wehave discovered that certain esters of thiolsulfonic acids .are surprisingly effective selective solvents for organic sulfur compounds in admixture with hydrocarbons, notably in certain petroleumoil fractions. We have .further found that said thiolsulfonic esters can beprepared relatively cheaply, have relatively mild corrosive properties permitting their employment in conventional equipment, are characterized by surprisinglylow or negligible solubility thereof -in the-raffinate phase produced by the extrac- 1 .tion process, are readily recoverable, and ha-ve physical properties which permit their employment as, selective extraction solvents for organic sulfur compounds at readily attainable temperatures. and-pressures. Moreover, the molecular weightand chemical'ccnstitutionof the thiolsulfonic esters can be varied to obtain tailor- ,made. extraction solvents best suited for the particular extraction operations as they arise.

It'is an object of thisinvention to provide a process for the selective extraction of organic sulfur compounds from their mixtures with hydrocarbons. Another object of this invention is to provide the art of selective extractionof organic sulfur compounds with novel solvents, vi a, certain thiolsulfonic esters. 'An additional object of our invention is to provide solvents for selective extraction processes characterized by high selectivity for organic sulfur compounds while at the same time exhibitinglittle or no solvent capacity for aliphatic hydrocarbons, h oth saturated and unsaturated. A further object .of. ourinvention is to provide :theart with novel selective.v extraction processes and solvent ere.- covery: procedures; These. and-otherobjectsof ,2 our invention, will be readilydiscerned from the ensuing. description thereof I and from" the appended drawing which is a schematic flovv sheet illustrating our process. v v H The novel solvents employed in the selective extraction process of this invention are thiolsulfonic esters containingbetween 2 and 20 carbonatoms, inclusive, per molecule and having the general formula: I

-,R1: Q2.- ,B wherein; R1 and -Rz'may be the same or different and are selected from the class consisting of hydrocarbon radicals and substituted hydrocarbon radicals. Ordina-rilm itis preferred to employ thiolsulionic esters wherein-R1 and -Rzare unsubstituted hydrocarbon radicals containing no aliphatic unsaturation, i. e., wherein-Brand R2 are selected from the class consisting-oisatu- 2n may bean alkyl radical, a cycloalkyl radicaL. a

cycloalkyl-alkyl radical, an aralkyl .radical,.aryl,

alkaryl or cycloalkyl-arylradical. TheuRland R2 radicals in theabove. formula maylcontain negative substituents such as halogen atoms, nitro groups, amino-groupsior thelike.

:Examples, given by .way ofillustration andnot Illustrative examples ,of

clopentyl,lmethylcyclopentyh cyclohex-yl, methylcyclohexyl, dimethylcyclohexyl. ethylcyclohexyl, ethylcyclopentyl, and .,@endomethylenecyclohexyl (bicyclo[2,2,1;lheptyl) and Z-methylbicyclo [2,2,1]heptyl. 1. Examples of; suita le Rror; R2 aralkyl-radicals in thelabove, general formula include .loenzyl, 2 phenylethyl, :2-phenylpropyl, w-xylyl, naphthomethyl, andthe like. ,Examples of suitableRi. or R2. cycloalkylealkyl radicals include. cyclohexylmethyl, oyclohexylethyl, cyclopentylpropyl, and :thelike. Examples, of suitable :Rlor. R2 ar-yl radicalstinelude phenyl, naphthyl and derivatives. containing: nuclearly'substituted chlorine atoms, nitro groups; etc. Examples of suitable R1 or :Rzialkaryl radicals for-,substitw ition inzthe above-generaiiormula are t olyl, ,xylyl,

dimethylphenyl, ethylphenyl, isopropylphenyl, butylphenyl, methylnaphthyl, .dignethylnaphthyl, andthe like. .Examples of suitable- Reser ists cycloalkyl-aryl radicals, include .oyclqhexylphenyl,

methylcyclopentylphenyl, cyclohexyltolyl, and the like. S fi e a e ioise egt vez :sdrefisimuem- -more or less of mites ployment in the extraction process of the present invention include the following esters of methanethiolsulfonic acid: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-amyl, octyl, dodecyl, hexadecyl, octadecyl; the corresponding esters of ethanethiolsulfonic acid; the corresponding esters, not however containing more than carbon atoms per molecule, of l-propanethiolsulfonic acid, Z-propanethiolsulfor'iic acid, butanethiolsulfonic acid, pentanethiolsulfonic acid, hexanethiolsulfonic acid, octanethiolsulfonic acid, dodecanethiolsulfonic acid, etc. Other specific examples include methyl benzenethiolsulfonate, methyl p e toluenethiolsulfonate, ethyl benzenethiolsulfonate, phenyl benzenethiolsulfonate, chlorophenyl chlorobenzenethiolsulfonate, benzyl benzenethiolsulfonate, phenyl, 3,5-dinitrobenzenethiolsulfonate, ethyl bis-benzenedithiolsulfonate, etc. It should be understood that we may employ mixtures of esters rather than individual esters. Because of their high selectivity and cheapness, we prefer to employ esters or" the above general formula wherein Bi and R2 are C1-C4 alkyl radicals.

Although there has been some dispute concerning the chemical structure of thiolsulfonic esters, sometimes called disuli'oxioes, the consensus of evidence favors the general formula which we have given above. The structures CH3SO2-SCH3 and C2H5SO2-SC2H5 have, for example, been assigned by us on the basis of infrared spectra showing strong absorption bonds at 7.6 and 8.8 microns, due to the SO2 group and the absence of absorption in the region of 9.1-101) microns, indicating the absence of the -SO- group. Structure assignment has also been based upon the discovery by us of a new acid-catalyzed addition reaction of thiolsulfonates to olefins to yield lA-sulfonethioethers, rather than the 1,4- disulfoxides which would be the reaction products expected from the symmetrical disulfoxide structure R1- SO-SO--R2. The selective solvents which we prefer to designate as esters of thiolsulionic acid are prepared preferably by the oxidation of the corresponding disulfide. They can be prepared non-catalytically with dilute nitric acid, that is, about 40% nitric acid or with hydrogen peroxide as oxidizing agents at ambient temperatures up to about 80 C. Other oxidizing agents may be used. The disulfides also may be oxidized catalytically using air or oxygen as the oxidizing agent and the higher oxides of nitrogen as catalyst as taught in U. S. 2,433,395. The esters of thiolsulfonic acid may also be prepared 'by other methods well known in the art.

It is not intended to imply that all the thiolsulfonates contemplated for use in this invention are precisely equivalent.

However, they are all generally useful and suitable for the purposes of the claimed invention.

The thiosulfonates defined by the above general formula are either normally liquid or relatively low melting solids and may usually be used for the purposes of the present invention without auxiliary solvents or diluents. However, because of their solubility in hot water, methanol, ethanol, benzol, etc., it may be desirable to employ the solvents of the present invention together with such diluents or co-solvents in order to modify the selectivity of the thiolsulfonates, to lower their melting points, or for other reasons. The amount of auxiliary solvents. employed can be selected with reference to specific cases; ordinarily, only between about 1 and about 20 weight per cent based on the thiolsulfonate will be employed. Anti-solvents or diluents may also be employed in the practice of the present invention. Thus, diluents such as saturated hydrocarbons may be added to the feed stock to be desulfurized or introduced directly into the extraction zone. In the process of the present invention the selective solvent is employed as a liquid, melt or solution; the feed stock may be charged to the process as a liquid or solution.

In general, the extraction operations of the present invention are conducted at temperatures between about -20 C. and about 150 C., the particular extraction temperature depending upon the specific thiolsulfonate solvent, the melting point of the solvent, whether or not it is used alone or with an auxiliary solvent or diluent, the degree and selectivity of extraction sought to be effected, etc.

The volume of selective solvent employed depends, among other things, upon the organic sulfur content of the feed stock, the temperature of operation and desired efficiency, but will generally fall within a range of about 0.2 to about 10 volumes of thiolsulfonate per volume of charging stock. Ordinarily, we prefer to employ between about 0.5 and about 2 volumes of solvent per volume of feed stock. Usually, pressures within the range of about 0 to p. s. i. g. are sufficient for this purpose, it being appreciated that the particular pressure necessary in a given case can readily be determined. The extractive process of the present invention is conducted under essentially neutral or slightly alkaline operating conditions.

Numerous hydrocarbon oil fractions derived from petroleum, coal, shale, etc., are known to contain organic sulfur compounds whose removal is desired in order to produce refined hydrocarbon oils. Such oils may boil within the boiling ranges of (and be generally characterized as) gasoline, naphtha, kerosene, gas oil, heater oil, furnace oil, diesel fuel, transformer oil, crude oil, lubricating oil, etc. The process of the present invention is applicable to the refining of gasoline boiling range hydrocarbon oils containing organic sulfur compounds, particularly thioethers or, in the case of sweetened gasolines, alkyl disulfides, and is applicable to such oils containing a substantial proportion of mono-olefinic hydrocarbons, as in the case of sweetened or unsweetened gasolines produced from sulfur-bearing crude oils, such as West Texas crude oil, by cracking or coking processes. The present refining process can be applied for the purpose of desulfurizing various petroleum stocks which are to be subsequently treated in refining or conversion operations in which sulfur or sulfur compounds are undesirable, for example, catalytic cracking operations, catalytic reforming operations, catalytic hydroforming operations, catalytic hydrogenation or dehydrogenation in the presence of sulfur-sensitive catalysts and the like.

The present process may also be applied to the refining of various coal tar fractions and coal tar distillates. In the refining of shale oil fractions the present refining agents serve not only to remove organic sulfur compounds from the feed stock, but also to remove oxygen compounds and nitrogen compounds. It should be understood that the above specific examples of charging stocks which may be refined in accordance with the present invention are illustrative only and are not intended to delimit the field of applicability of the process of the present invention.

eyeeaass;

5. The present invention can be carried out; in batch, continuous or semi-continuous operating cycles; and in one or more stages, employing contacting and separation equipment suchas has heretofore'been employed in the selective solvent refining of-petroleum-lubrica-ting oil stocks or in effecting the alkylation of-isoparafiinic hydrocarbons-with olefins in the presence of liquid acid catalysts. It should be understood that: the specific equipmentemployed forms nopart of the present invention-and that. any equipment adaptablefor the purposes of contacting the solventwith the" hydrocarbon charging stock and thereafter-separating-an extract phase from there fined; charging stock can be employedfor the purposes of the invention. The data in the tahle afforda comparisonof the performance of methyl methanethiolsulfonate in cracked cycle stock extraction with that of nitromethane, furfural', dimethy-lformamide, S02, and diethylsulfoxide, whichare among the most highly-regarded'solvents for'the extraction of sulfurcompounds from the type of" feed stock here'-under-consideration. Asa measure of the selectivity of'the-solvents for the extraction of sulfurcompounds, the so-called sulfur'selectivity factor (SSF) is-determined in accordance with the following equation:

ercent Sin feed,-,D .rcentSin reaifinate S'S'R'P'J Volume percent extracted X104 ABLE.

Volume percent Solvent extract fivity I ii fi factor Methyl methauethiolsulfonata 16 240 i wnet ne; 200 Furfural, 26 220 Dimethyl formam da. 40 160 Sulfur dioxide 35 210 C,L l- 'S0CzHs 36 160 Thusimethyl methanethiolsulfonate was superior in sulfur selectivity: to all of the excellent liquid olv nts.

The lightcatalytic cycle stock employed in cer tain of theexampleswas derived fromthe cata lytic cracking, of West Texas gas oil inthe presence of natural claycatalyst andhaolthe followin: propert es:

A. s. T. M; distillation Volume percent di til d:

The following examples are intended to illustratebut not necessarily to limit the invention:

Example 1 Light catalytical-ly cracked-cycle oil having" the m'qperties set forth in thesabove table was agiyielded 58 volumes of a dark-colored bottom or extract layer and 42 volumes of a top or raifinate, layer of much lighter color than the feed stock. The raffinate layer was washed briefly with boileing Water and was found to contain 0.72 weight per cent. sulfur as against 1.10 weight per cent sulfur in the feed stock; thiscorresponds to desulfurization of the feed stockwith th pro-' duction of 16% of extract, or a sulfur selectivity; factor-of about 229. When a further portionof the raffinate' layer was washed with cold aqueous: caustic solution, then with water and filtered; its sulfur content was reduced to 0.65 weight; per cent, corresponding to 41% desulfurizationioran. overall sulfur selectivity factor of about255.

A mixture of equal volumes of the above der scribed catalytic cycle-stock and phenyl benzene.- thiolsulfonatewas agitated to obtain contact over a period of five minutes at room temperature afterwhich itwas permitted to separate to form two layers. The extractant phenyl benzene,- thiolsulfonate was preparedby oxidizing diphenyl disulfide with hydrogen; peroxide and was used in this experiment as. a super cooled liquid.- Uponseparation of the mixture, a rafiinate layer amounting to 30% of the total volume of the mixture was purified by crystallization'ofa minor amount extractant therefrom This rafiinate had a sulfur content of 0.66% as contrastedwith a sulfur content of 1.10% for the raw unextracted catalytic cycle stock. Thus a yield of about 60%; of desulfurized oil wasobtainedh A sulfur selectivity factor of 106 is indicated.

Example 3 A mixture of equal volumes of methyl disulfide and normal heptane was agitated for 10 minutes at room temperature with. an equal volume of methyl methanethiolsulfonate. From 5; volumes of charging stock there was obtained a rafiinate layer of 2.? volumes. Two volumesof the raf finatelayer were then treatedwithconcentrated (37.7 %:)v aqueous hydrochloric acid to remove. 01 volume of the solvent which was presenttherein. The raiiinate thus obtained had a; refractive indexof. a 1.4159 while the refractive, indices. of the feed stock and of neheptane were 1.4543 and 1.3879, respectively. Thus, about desulfur-, ization was obtained with about 48% extraction of the feed stock into the extractv layer, corresponding to a sulfur selectivity factor of about: 115..

An illustrative flow process and equipmentare indicated in the figure. The. hydrocarbon mixe tureto be extracted, containing sulfur: come pounds, for example, a, light cycle stock from silica-alumina cracking of :a West Texas gasoil; is passed through valved line it into the-cone tacting' zone H. The feed stockis preferablydried and, if it contains hydrogen sulfide,- is treated toeffect its removal, e. g., by washing with caustic, ethanolamine, dimethyl'eth'anolamine, etc.

We may employ conventional contacting and separation equipment such as has heretofore been employed in effecting selective solvent ex traction of lubricating oils, illuminating oils, etc, or in the processes for the extractive distillation of hydrocarbon-oils. The contacting equipment may comprise a vertical tower, which is preferably provided with packing or spacing materials to insure thorough contacting of the hydrocarbon feed stock and the thiolsulionate solvent. Suitable materials of construction for the contacting zone are aluminum and stainless steel, although it should be understood that we may employ other construction materials, for example, glass-, ceramicor carbon-lined iron towers. Suitable spacing materials comprise shaped fragments, for example, Berl saddles or Raschig rings made of carbon, porcelain, glass, aluminum, stainless steel, etc.; stainless steel jack chain; stainless steel or aluminum screens Which may be shaped, for example, in the form of Scofield, McMahon or Stedman packing, etc. If desired, the contacting tower may be jacketed or provided with heat exchange coils to permit maintenance of the desired temperature.

In a desirable method of operation, the feed stock is passed into the lower portion of zone ll against a counter-flow of a thiolsulfonate, for example, methyl methanethiolsulfonate, which is introduced into the upper portion of tower H through valved line i2. Diluents, e. g., pentane or hexane, or modifying solvents, e. g. ethanol or benzol, may be introduced with the feed stock, the thiolsulfonate solvent or separately through a line not shown, into zone IE. Alkaline conditions during extraction can be maintained by introducing ammonia (gas) into zone H (by a line not shown).

The contacting of the thiolsulfonate and hydrocarbon feed stock results in the production of rafiinate and extract phases whose common boundary or interface is indicated at 13. The countercurrent extraction zone may be operated with either the feed stock or solvent as the continuous phase. In the mode of operation, illustrated in the drawing, the extract phase is shown as the continuous phase through which the hydrocarbon feed stock is introduced as the dis persed phase.

The rafiinate phase forms a supernatant layer above interface 13 in zone H whence it is discharged, together with the diluent employed, from said zone through valved line 14. The rafiinate phase is characterized by a substantially reduced content of organic sulfur compounds as compared with the feed stock. It should be understood, however, that the raffinate phase may be further treated to reduced its content of organic sulfur compounds, if it is so desired. For this purpose, a portion at least of the raffinate phase may be recycled from line M by a line not shown to re-enter zone H with fresh feed stock. Alternatively, or in addition, the rafiinate in line 14 may be sent to another contacting zone, identical in all substantial respects with zone I l, for treatment in a second stage with fresh solvent, which may be the same thiolsulfonate or a different thiolsulfonate from that passing into line l2, or may be an entirely different type of solvent, e. g. liquid hydrogen fluoride, HF-BF3, liquid S02, phenol, furfural, dimethylformamide, bis-(beta-chloroethyl) ether, etc. It should be noted that further extraction of the rafiinate passing through line 14 with solvents different from the thiolsulfonate passing through line I2 is greatly facilitated by the fact that the thiolsulfonate is substantially insoluble in said raifinate, averting the necessity of special procedures for the removal of thiolsulfonate from said raffinate. Small amounts of thiolsulfonate entrained in the rafiinate can be removed by washing with hot water or aqueous hydrochloric acid.

The extract phase, a solution of organic sulfur compounds in the thiolsulfonate solvent, is withdrawn from the lower end of tower H through valved line l5, whence it is passed into separation zone [6. If desired, a part of the extract phase may be recycled from line l5 to feed line I0 by means of a line not shown in the drawing. Zone It may be a separating vessel into which hot water or aqueous extractants are introduced by valved line H, in suitable amounts, e. g. between about 0.5 and about 3.0 volumes per volume of extract, at temperatures between about 20 and about C. to effect the resolution of the extract into an aqueous thiolsulfonate layer and a layer containing organic sulfur compounds and co-solvent employed in the extraction operation. Methyl methanethiolsulfonate is soluble to the extent of about 15 g. per 100 g. of water at 65 C. and about 6 g. per 100 g. of water at 20 0.; its solubility in 37.7% hydrochloric acid is about 10 times its solubility in water at the same temperature and the HCl solution of the thiolsulfonate can be resolved into two layers by blowing off 1101 gas. Alternatively, the separation zone It may take the form of a distillation vessel, preferably a steam distillation vessel in which the sulfur compounds are vaporized and pass overhead, usually as azeotropes with water, through line l8 into a settling vessel I9, whence the water layer is withdrawn through valved line 29 and sulfur compounds are withdrawn through valved line 2!. The extracted materials may be employed as plasticizers for vinyl resins, natural and synthetic rubber, asphalts, etc.

A bottoms fraction containing the thiosulfonateis withdrawn from zone I6 through valved, insulated line 22 into a settler 23 provided with weir 24 and cooling coil 25. The temperature of the aqueous solution of thiosulfonate in settler 23 is reduced to about room temperature or even to a lower temperature, e. g., down to about 10 C. in order to reduce the solubility of the thiOSlll-r fonate solvent in said aqueous phase. If desired, CaClz, NaCl or other salts may be added to the aqueous phase in settler 23 in order to reduce the solubility of the thiolsulfonate solvent therein. Two immiscible liquid layers are produced in settler 23, one of which is water or an aqueous salt solution and the other of which comprises essentially the thiosulfonate solvent. The thiosulfonates are in general of higher specific gravity than water but may be of lower specific gravity than aqueous salt solutions. The two layers are separately withdrawn from settler 23 at the appropriate points. For illustrative purposes, in the figure, an aqueous salt solution is shown being withdrawn from settler 23 through valved line 26 and the thiosulfonate solvent through valved line 21, whence it may be recycled wholly or in part through valved line 28 and manifold 29 to line l2 and thence to extraction column H. Preferably, at least a portion of the thiolsulfonate solvent is directed from line 2'! into a distillation column 30 provided with a heating or reboiler coil 3|. Column 36) can suitably be a vacuum still from which steam can be separated from the wet solvent and removed overhead through line 32 into a barometric condenser 33. The dried solvent is discharged as bottoms through line 34 into manifold 29 for recycle to the extraction zone ll.

Alternatively, the recycle stream of solvent may be dehydrated in column 30 by azeotropic distillation of water therefrom with various azeotroping agents, e. g. benzene, toluene, n-heptane, ethyl acetate, etc.

Although the drawing represents a continuous countercurrent extraction operation, it will be apparent that the process of the present invention is amenable to batch processing, multi-unit operation, concurrent flow of solvent and feed stock, the use of knot-hole or other mechanical mixers for feed and solvent in series with one or more settling zones and other variations that will no doubt occur to those skilled in the art without departing from the spirit of this invention.

Having thus described the process of our invention, what we claim is:

1. A process for the extraction of an organic sulfur compound from a mixture thereof with hydrocarbons, which process comprises contacting said mixture with an ester of a thiolsulfonic acid containing 2 to 20 carbon atoms per molecule and separating a raifinate phase from an extract phase comprising said ester and said organic sulfur compound.

2. The process of claim 1 wherein said mixture comprises a cracked gas oil containing organic sulfur compounds.

.3. A process for the extraction of an organic sulfur compound from a mixture thereof with hydrocarbons, which process comprises contacting said mixture with an ester of a thiolsulfonic acid containing 2 to 20 carbon atoms per molecule in liquid condition at a temperature between about -20 C. and about 150 C., and separating a raflinate phase from an extract phase comprising said ester and said organic sulfur compound. 4. The process of claim 3 wherein said ester has the formula R1SOZ-SR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

' '5. The process of claim 3 wherein said mixture comprises a cracked gas oil containing organic sulfur compounds and said ester has the formula R1SO2-SR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

6. The process of claim 3 wherein said mixture comprises essentially a saturated hydrocarbon and said ester has the formula R1SO2-SR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

7. A process for the extraction of an organic sulfur compound from a mixture thereof with hydrocarbons, which process comprises contacting said mixture with an ester of a thiolsulfonic acid containing 2 to 20 carbon atoms per molecule in liquid condition, separating a raflinate layer from an extract layer containing said ester iii and said sulfur compound, selectively extracting said ester from said extract layer with an aqueous extractant at a temperature between about 20 and about C. to produce an aqueous ester, drying said aqueous ester and recycling the resultant dried ester to further contact with said mixture.

8. The process of claim 7 wherein said ester has the formula R1SO2-SR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

9. The process of claim '7 wherein said mixture comprises a cracked gas oil and said ester has the formula RiSOzSR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

10. A process for the extraction of a cognate organic sulfur compound from its mixture thereof with a hydrocarbon, which process comprises contacting said mixture in the absence of a strongly alkaline metal hydroxide with an ester of a thiolsulfonic acid containing 2 to 20 carbon atoms per molecule, and separating a refined, substantially desulfurized hydrocarbon liquid layer from an insoluble extract liquid layer comprising said ester and said organic sulfur compound.

11. The process of claim 10 wherein said ester has the formula RISOZSR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

12. The process of claim 10 wherein said mixture comprises a cracked gas oil containing organic sulfur compounds and said ester has the formula R1SOz-SR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

13. The process of claim 10 wherein said mixture comprises a sweetened gasoline.

14. The process of claim 10 wherein said mixture comprises a sweetened gasoline and said ester has the formula R1SO2SR2 wherein R1 and R2 are alkyl radicals containing 1 to 4 carbon atoms.

15. The process of claim 10 wherein said mixture comprises a thioether.

16. The process of claim 10 wherein said mixture comprises a disulfide.

WILLIAM F. WOLFF. CARL E. JOHNSON.

References Cited in the file of this patent FOREIGN PATENTS Number Country Date 830,532 France May 16, 1938 OTHER REFERENCES Gilman, Organic Chem., vol. 1, 2nd ed., page 

1. A PROCESS FOR THE EXTRACTION OF AN ORGANIC SULFUR COMPOUND FROM A MIXTURE THEREOF WITH HYDROCARBONS, WHICH PROCESS COMPRISES CONTACTING SAID MIXTURE WITH AN ESTER OF A THIOLSULFONIC ACID CONTAINING 2 TO 20 CARBON ATOMS PER MOLECULE AND SEPARATING A RAFFINATE PHASE FROM AN EXTRACT PHASE COMPRISING SAID ESTER AND SAID ORGANIC SULFUR COMPOUND. 